Hey, I was in the same boat as you last year where I'd always be one or two marks off an A. I'd say do one past paper in timed conditions and mark it as harshly as you can - then identify what topics you got wrong. The extended responses are also a great way to boost our mark, I'd suggest using them to aid your revision since they have the wording. There are also YouTube videos online from 'Higher Human Biology' Channel which are pretty good. If you can afford it or see if you can get an online copy of Leckie and Leckie's SQA Higher Human Biology since most of the exercises go over specific wording that would be accepted by SQA. It may also be helpful to go on Scholar for Higher Human and do the tasks there - Scholar does use the SQA wording so I'd highly recommend.
In terms of flashcards, of course you only have a month so maybe I'd suggest searching on quizlet and using someone's there. Alternatively, you could go on blooket and search Higher Human Biology and work through some of them if you're a bit low on willpower that day. Good luck for your upcoming exams!